This invention relates to blind rivet setting tools and particularly to an apparatus for addressing the problem of rivet mandrel jamming in such tools.
Rivet tools of this kind generally operate from a pressurized air supply that is controlled by a trigger lever. When the lever is operated pressurized air pushes an air piston which in turn acts on a hydraulic ram assembly that forces hydraulic fluid from a reservoir in the handle of the tool into a main hydraulic bore where it moves a hydraulic piston with an attached rivet pulling mechanism rearward. As the pulling mechanism with its pulling jaws move rearwardly the jaws close on and grip the rivet mandrel and set the rivet. When the trigger is released, the hydraulic piston is pushed forward to the starting position so that the hydraulic fluid is also forced back, returning the hydraulic fluid and the air piston to the starting position. When the hydraulic piston is fully returned the broken rivet mandrel is released as the pulling jaws are forced open by acting against the nose piece of the tool. The spent mandrel is then drawn out of the tool through a vacuum passageway and deposited in a mandrel collection container.
The spent mandrels can jam in the passageway on their way to the mandrel container for any number of reasons, including dirt and oil build up in the passageway, a kink in the collection hose, insufficient vacuum due to a leak, a bent mandrel in the mix, or simply the changing shape and direction of the passageway combining at times to defeat mandrel exit, especially in the vicinity of the connection between the exit hose and the tool.
Normally one would shake or twist the collection hose to clear an obstruction and failing that dismantle sections of the tool in order to gain access to the jammed area so as to manually clear the passageway. A known method is described in the patent to Ebbert et al (4,130,006) in which an axially shiftable tube is provided in the tool passageway where it is expected jamming might occur. Reciprocating the tube, it is suggested, will shake the jammed mandrels free. In each case, however, chance as much as management plays a role in freeing the jam, which means that jam clearance is not always achieved in a timely and efficient manner.